This invention relates to the polymerization of ethylene to form ethylene polymers including both homopolymers and copolymers of ethylene and a higher 1-olefin using a chromium-containing catalyst. Supported chromium-containing catalyts can be used to prepare ethylene polymers and copolymers in a hydrocarbon solution as is well known in the art. Such polymers generally have a small amount of unsaturation. Even when hydrogen is utilized during polymerization for molecular weight control, hydrogen acts primarily as a chain-transfer agent and hence significant hydrogenation of the polymer does not occur in the presence of the olefin monomer. While polymers produced from conventional systems have excellent characteristics and have found wide utility in the art, the presence of unsaturation does have an unfavorable effect on certain properties such as dielectric loss at high frequencies and high temperature stability. The relationship of unsaturation to stability is disclosed in Hogan, U.S. Pat. No. 3,513,152.